Version 1.6 1-28-1998
TOBIN International, Ltd.
16260Broadway, Suite 500
Denver, Colorado 80202-4725
(303) 831-3555
1. Introduction *
1.1 Digital Cartographic Data from the USGS *
1.1.1 DLGs from USGS 1:100,000-scale quadrangles *
1.2 National Geographic Names Data Base *
2. Processing the USGS Digital Data *
2.1 TOBIN's DLG Interpreter *
2.2 TOBIN's GNIS Interpreter *
2.3 The External Formats *
2.3.1 InfoBase in particular *
2.4 Future Enhancements *
2.4.1 Association of Names and Features *
2.4.2 State and County Codes *
3. The Feature Codes *
3.1 Boundaries *
3.2 Hydrography *
3.2.1 Ocean Features *
3.2.2 Lake Features *
3.2.3 Shorelines *
3.2.4 River Features *
3.2.5 Manmade Watercourses *
3.2.6 Special-Use Water Features *
3.2.7 Miscellaneous Hydrography *
3.3 Roads and Trails *
3.3.1 Classification of Roads *
3.3.2 Highway Names *
3.3.3 Roads *
3.3.4 Ends of Roads *
3.3.5 Bridges, Tunnels, etc. *
3.3.6 Miscellaneous Road Features *
3.4 Railroads *
3.4.1 Tracks *
3.4.2 Yards and Stations *
3.4.3 Miscellaneous Railroad Features *
3.5 Pipes, Transmission Lines, and Miscellaneous Transportation *
3.5.1 Electrical Power Features *
3.5.2 Oil and Gas Features *
3.5.3 Miscellaneous Transportation Features *
3.5.4 Aviation Features *
3.6 Other Manmade Features *
3.7 Natural Features *
InfoBase Class and Sub-Classs Codes *
TOBIN's Culture databases represent a merging and processing of two data sets originally created and distributed by the National Cartographic Information Center (NCIC) of the United States Geological Survey (USGS) as part of the National Mapping Program. The two data sets are, first, the Digital Line Graphs (DLGs) digitized from the USGS 1:100,000-scale quadrangle series, and second, the National Geographic Names Data Base (which is one of four databases that make up the Geographic Names Information System, or GNIS).
1.1 Digital Cartographic Data from the USGS
The USGS is in the process of digitizing various layers of data from various series of their maps. Most of the projects under way are still far from complete; and some of the projects (those digitized from 1:2,000,000-scale sources) have a level of accuracy deemed unacceptable for TOBIN's purposes. So, for now, TOBIN offers only a few of the data sets the USGS has developed; as more of the USGS's large-scale projects near completion, more data layers will be made available in TOBIN's external formats.
The primary USGS project that is now complete (or nearly complete) and sufficiently accurate for TOBIN's purposes is the digitization of various data layers from the 1:100,000 scale topometric quadrangles. Complete or near-complete coverage of the United States from sources in this series is currently available for four data layers:
(This last category is sometimes lumped together with roads and railroads and considered a single data layer, transportation. The USGS sells all the transportation for a given area as a unit; and while the three layers are kept in separate files, they are collected -digitized - at the same time.) Several additional layers (hypsography, vegetative land cover, nonvegetative land cover, survey control and markers, boundaries, manmade features, and the United States Public Lands Survey System) are planned and will perhaps become available at some later date. (The USGS has some of these layers available now for limited areas of the country, but the coverage is spotty at best, and TOBIN does not yet make them available.) Additionally, the USGS is digitizing or plans to digitize all the data layers from source maps in the 1:24,000-scale series; but none of the layers even approaches complete national coverage yet.
1.1.1 DLGs from USGS 1:100,000-scale quadrangles
The USGS uses both manual and automatic methods to digitize the 1:100,000-scale (30 minute by 60 minute) quadrangles, eventually generating DLG files that are entered into the National Digital Cartographic Data Base (NDCDB). (These files are designated as being "DLG-3" files, meaning that they contain the full range of possible attribute codes -- with some specific exceptions -- and are topologically fully structured. The USGS originally had intended, but then decided not, to produce DLG-1 and DLG-2 files as well.) The manual digitizing method takes place primarily on Altek and Intergraph digitizing systems, and the automatic method on a Scitex raster scanning and editing system. In both methods, the operator makes many judgement calls as to how to interpret the source document (the 1:100,000-scale quadrangle); he or she is supposed to follow the standards set forth in the documents "Digital Line Graphs from 1:100,000-Scale Maps" (1985, revised 1989) and "Standards for Digital Line Graphs, Part 3: Attribute Coding" (1985, revised 1990, and now considered to supersede the first-mentioned document). Both documents are available from the USGS National Mapping Division. Some of the feature and attribute codes used in 1985 and in earlier versions of the NDCDB are no longer used; some are now used differently than they were; and some new attributes have been defined in the 1990 document.
Various factors make the available DLGs somewhat less than uniform in the quality and characteristics of their cartography. Note that even if the operator follows all the applicable standards precisely, his or her results cannot be any more accurate or consistent than his source documents, which were compiled onto paper over many years by hundreds of different cartographers, with widely varying standards and practices. Also, the various DLG files available have been digitized from those 1:100,000-scale source maps at various times over the last ten years or so, and so (because the standards for coding DLGs have changed at least twice during that time) will be slightly inconsistent from one to another. And finally, different operators will interpret ambiguities differently, whether on the source documents or in the digitizing instructions.
While the USGS does plan to "clean up" data discrepancies at the edges of maps, very little has yet been done along those lines. So a road, for instance, may seem to jump to one side as it crosses the boundary from one map to another. Another source of apparent map-edge discrepancies is the variation in the age of the 1:100,000-scale maps -if a feature (a pipeline, for instance) was built after map A was compiled, but before map B, the user of a DLG file constructed from the two maps will see the pipeline apparently stop short at the point where it crosses from map B to map A.
The DLGs digitized directly from 1:24,000-scale series source maps (and from some maps in the limited 1:25,000-scale series) are very similar to the DLGs from smaller scale sources, with the following exceptions: the coverage area currently available is much smaller, for all data layers; there are a number of additional feature codes defined to represent the larger range of features visible on the larger-scale maps; and there is (of course) a much greater density of data per geographic area.
TOBIN does not at this time make available any of the USGS data produced directly from sources in this series. But the additional feature codes that will be needed have been defined in anticipation, and are discussed later in this document. Whenever one of these additional feature codes is defined, it is specified as applying only to 1:24,000-scale sources.
1.2 National Geographic Names Data Base
The NGNDB was compiled originally (beginning with Massachusetts in 1968) from the USGS 1:24,000 and 1:25,000- scale Topographic quadrangle series wherever those series were available; and (where the large-scale maps weren't available) from the 15-minute quadrangles (1:62,500-scale) and other available sources. This compilation was performed by the Geographic Names Information Service office (GNIS) of the USGS; and the GNIS makes them available now in digital form. After compilation, the names were edited by comparison with the records of the U. S. Board on Geographic Names (BGN) and other authoritative sources. This editing process is ongoing.
The initial collection of data from the published USGS maps (designated "Phase I") was completed for the entire United States in 1981. Phase II of the compilation process, the collection of additional toponymic data from other sources, including maps, charts, texts, and historical sources, is continuing.
The names in the NGNDB are indexed to a geographic location - usually the exact location (for small features) or the approximate center (for large ones) of the feature the name refers to - and given a feature code, one of 63 classes of named objects, that serves to specify what kind of object the name applies to. (Other information is included as well; but for simple cartographic purposes only the name, location, and feature code are meaningful.) But note that there is no explicit relationship between names from the NGNDG on the one hand, and DLG features digitized from source quadrangles on the other. Usually the given location for the name will be very close to or conincident upon the location of the digitized feature, but not always. Sometimes a name will appear that corresponds to no digitized feature, and digitized features frequently have no corresponding name in the NGNDB.
Names of roads and highways are not included in the NGNDB, but are available in the DLGs of the "roads and trails" data layer.
2. Processing the USGS Digital Data
TOBIN obtains the NDCDB and NGNDB files on magnetic tape directly from the USGS. The files are loaded from tape and then translated by the DLG and GNIS Interpreter programs into the format of TOBIN's in-house database; from the inhouse databases, the data can be formatted in a number of external (delivery) formats, InfoBase and ASCII-X in particular.
Subject to the various external formats' limitations, TOBIN passes the original data through the two translation processes (from the DLGs and GNIS formats to the TOBIN database, from the TOBIN database to external formats) with as little distortion, filtering, or interpretation as possible. For this reason, any data irregularities or idiosyncrasies (or indeed, errors) that appear in the original DLG and NGNDB files are faithfully reproduced in our output files, unless TOBIN concludes that the apparent errors stem from a corruption of the digital data files, in which the errors will be corrected before the data is translated, formatted, and released.
While TOBIN would like to perform as little manipulation of the incoming data as possible, certain facts about the USGS DLG files make a certain level of interpretation either absolutely necessary or definitely desirable. This interpretation (and simple translation into TOBIN's internal database format) is performed by TOBIN's DLG Interpreter program.
A Digital Line Graph in general (a mathematical construct belonging to the discipline of topology), among many other odd features, has the two properties that no two areas of the graph may overlap, and no two lines may cross. These properties make the DLG representation of geographic information problematic at best, since in the real world (and hence on most normal maps) areas do merge or overlap (as, for instance, a portion of a lake designated as containing navigational hazards overlaps the lake itself), and linear features (roads, for instance) do cross each other. But in a DLG the hazard area and the lake would be two distinct non-overlapping areas; and the pieces of a road between each pair of intersections would be coded as distinct lines. Similarly, a marsh area with a stream running through it would be coded as two separate marshes bordering each other at the stream. None of all this reflects the real world or how we usually think about it.
Other features of DLGs make them difficult, or even inappropriate, to use for mapping. The edge of the map is represented in the DLG as a "Closure Line"; this code is also used to mark the places where two areas border each other, even when there is no corresponding geographic feature (as, for instance, where a river empties into a bay). A limitation in the digitizing software used by the USGS introduces another useless code, the "Processing Line". Yet another is the "Extension Line", used to represent parts of features not actually shown on the source maps because of crowding or masking by other drawn features. Then there are the feature codes. Rather than having separate codes for lakes, salt lakes, and intermittent lakes (for example), the USGS DLG specification defines (sensibly enough) one code for "Lake", another for "Salt", and another for "Intermittent". An intermittent salt lake would have all three feature codes; a salt-water well would have the code for "Well" and the one for "Salt"; and so on. This scheme works fine if (but only if) the data format being used has an indefinite record length. If, on the other hand, the data is to be handled in the more usual, fixed length kind of records, distinct feature codes are needed for each possible feature type. Both InfoBase and ASCII-X are fixed-record-length formats, and so the multitude of possible combinations of feature codes in the DLG format are combined into distinct codes by TOBIN's DLG Interpreter program.
Besides interpreting DLG files into a form that makes better sense for mapping and plotting purposes, the DLG Interpreter program (along with its pre and post-processors) organizes the incoming culture data into one-degree squares and archives it onto magnetic tape both in its original DLG format and in the TOBIN internal database format, from which it can be output in InfoBase or ASCII-X or some other external data format. Typically at the same time, an InfoBase output version of the one-degree database is made and archived, and a check plot prepared from the InfoBase file -this additional processing makes it far easier for TOBIN to catch data discrepancies and problems early on, and assure better-quality output data to clients. If any problems with the data are observed or suspected, a plot is prepared from the internal database version of the same data to see whether the problem is with the data or with the formatter. If the problem is in the data, steps can be taken either in-house or in cooperation with the USGS to resolve it; if the problem is in the formatter, the bug is reported to TOBIN's software department, and is fixed as promptly as possible. In either case, an internal hold is placed on the data to prevent its being delivered to clients until all observed problems have been resolved.
At the same time at which the DLG files are being interpreted, statistics are gathered regarding the size of the database, the mix of data types observed, point counts, etc. Besides their use in satisfying idle curiosity, these numbers are used to assure that no data is disappearing between the time it's read in by the DLG Interpreter and the time it's output by the external formatters.
The files that make up the NGNDB are provided by the GNIS in several different formats. TOBIN has written interpreter programs to translate the NGNDB files into the internal database format without losing any pertinent data. In many cases, the feature classes assigned to the name records are similar to feature codes used in the DLG files; but in many other cases they are quite different. For instance, there is a GNIS feature class "gut" defined as a "relatively small coastal waterway connecting larger bodies of water or other waterways". This same feature would have been coded as "Ocean" in the DLG format, but a feature's being classed as a "Gut" certainly carries additional information besides the fact of its being part of an ocean. Or, as another example, the GNIS feature class "crossing" applies to "a place where two or more routes of transportation form a junction or intersection"; but there is no such code in the DLG format -the place where two roads come together isn't usually given any attribute code at all. In spite of the difficulties, though, one way or another, all the names in the NGNDB are interpreted and put into the TOBIN internal database format.
Each external format program (or "formatter") reads culture data from TOBIN's internal database and creates distribution files in a format which can be more easily read and manipulated. In some cases (InfoBase in particular) the data correspondence between the internal database and the external format is very nearly one-to-one; in other cases, some aspects of the data cannot be expressed in the target format. But in every case, the distribution files (called "dot-x" files because their filenames typically end with the extension ".x") are, as nearly as may be (given the constraints of the individual formats) complete representations of the data contained in the internal database.
The current implementation of the Culture product in the InfoBase external format leaves certain of the defined InfoBase fields blank; and certain other fields can contain only a subset of the range of values defined. Here follows a list of the fields in which the user may see something other than what he might expect from a reading of the InfoBase format definition. Refer to the document "TOBIN InfoBase Data Distribution Tape Format"; section 3.6, "Culture Data (Data Type 3)".
Header Page - Record Type 0:
Point Type Currently always set to "30", "Single Line", even though in some cases (for instance, rivers where both banks are represented) there may be "penup" markers embedded in the line, indicating that in fact the entity is made up of multiple lines.
Survey Name Filled with blanks.
Block Name Filled with blanks.
Section Number Filled with blanks.
State Code Filled with blanks, but see "State and County Codes" under "Future Enhancements" below.
County Code Filled with blanks, but see "State and County Codes" under "Future Enhancements" below.
Railroad District Filled with blanks, but see "State and County Codes" under "Future Enhancements" below.
Note that no entities are coded as "Single-Point Entities", even if they actually contain only a single point.
Annotation Records -Record Type 5:
The Annotation records contain various information about the features; for instance, the name of a road or highway, or the surface elevation of a lake.
Annotation records are also used to contain the names obtained from the NGNDB files. In this case, there is usually only one Header Record for each named feature type, with the individual names appearing as individual Annotation records. For instance, if a one-degree database contained three names designated "canal", there would be a single Header record (Record Type 0) specifying the Class and Sub-Class codes for "Canal", followed by three Annotation records (Record Type 5) each containing and specifying the location of one of the three names. See also "Association of Names and Features" under "Future Enhancements" below.
A special annotation, an arrow "-->" is used with a river feature to designate the direction of its flow. The arrow is placed in the river, near the upstream end of whatever portion of the river is present in the current database, and is oriented so that it points downstream.
Text Records -Record Type 7:
The text portion of Text records contains collateral information on some features. For instance, the count of tracks of a railroad or lanes of a highway is output in a Text record; the text would read, for instance, "8 Lanes" or "4 Tracks". Additionally, for railroads, Text records can exist reading "Rapid Transit", "Private", or "U. S. Government"; for roads they can read "Toll", "Private", or "Proposed". If more than one of these "modifiers" exists and is to be applied to the same feature, there will be one Text record for each condition specified.
2.4.1 Association of Names and Features
Among TOBIN's planned enhancements of the Culture product is the association of GNIS names with the features they denote. This association will be based on an examination of the feature codes and the geographic locations associated with the names, and will take place automatically.
We anticipate that the association will be incomplete - that is, not every name will be assigned to a feature, and not every feature will be named. But within the limits imposed by the fact that the GNIS and DLG files use entirely different feature coding schemes, and the fact that the two sets of data have been collected independently and according to different criteria, it is expected that users will find the association of names and features to be useful.
The NDCDB and NGNDB files frequently have State codes (and in the case of the NGNDB, County codes as well) associated with the various geographic features represented or named. Unfortunately, the State and County codes are frequently incorrect. So, for the time being, the TOBIN external format files, which do have fields set aside for State and County codes, do not have those fields filled in. As a future enhancement to the Culture product, TOBIN intends to develop software to determine, for each feature, what state and county it is in, and to fill in the State and County Code fields of the external format records correctly, based on that determination. (In the case of Texas data, the field for Railroad District, if the format has such a field, will be filled in as well.)
This section describes and defines each of the feature codes represented in the TOBIN internal database, and hence in the external format files received by TOBIN's clients. Care has been taken to code explicitly any expected or commonly occurring combination of features and attributes (such as a dry well, or an elevated railroad). Very rarely, combinations of characteristics may occur in the DLGs for which no code is defined. In these cases, in the InfoBase format only, a Text record will be added to the entity in question; the Text record will contain the attribute ("Underpassing", "Intermittent", or whatever) that could not be coded directly.
For each feature code defined, there is one subsection below which tells:
The following subsections are arranged in order according to their InfoBase "Class" codes (which correspond to the "major codes" in DLG format), and within each class by the InfoBase "Sub-Class".
The following feature codes are currently used only for certain feature names derived from the GNIS NGNDB files. TOBIN does not at this time process or distribute any DLG data in the Boundaries layer.
Park.
A GNIS Feature Class "park" (with the listed synonyms "national historical landmark", "national park", "State park", and "wilderness area") is defined as a "place or area set aside for recreation or preservation of a cultural or natural resource and under some form of government administration; not including National or State forests or Reserves". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 22
InfoBase Class: 20
InfoBase Sub-Class: 01
Unknown.
A GNIS Feature Class "civil" (with the listed synonyms "borough", "county", "municipio", "parish", "town", and "township") is defined as "a political division formed for administrative purposes".
Another GNIS Feature Class "forest" (with the listed synonyms "national forest", "national grasslands", and "State forest") is defined as a "bounded area of woods, forest, or grassland under the administration of a political
agency.
A third GNIS Feature Class "reserve" is defined as "a tract of land set aside for a specific use (does not include forests, civil divisions, parks)".
Any GNIS names in any of these classes will be assigned the feature code for an "Unknown" boundary.
ASCII-X Logical Level: 22
InfoBase Class: 20
InfoBase Sub-Class: 08
3.2 Hydrography
Hydrography includes streams and rivers, lakes and ponds, wetlands, coastal water, water used for transportation, and related features. These features sometimes have a surface elevation marked on the source maps; when this happens, an Annotation record showing the elevation accompanies the feature.
Ocean , bay, estuary, gulf, or sea.
A seaward area of water. The inland extent is defined at the place where a river reaches a width of one nautical mile (6,080 feet) with no further constrictions downstream, if the conformation of the land and water do not otherwise make the division between river and ocean obvious.
A GNIS Feature Class "sea" (with the listed synonyms "gulf" and "ocean") is defined as a "large body of salt water" (which, by the way, would seem incorrectly to include the Great Salt Lake, for instance). Another GNIS Feature Class "bay" (with the listed synonyms "arm", "bight", "cove", "estuary", "gulf", "inlet", and "sound") is defined as an "indentation of a coastline or shoreline enclosing a part of a body of water; a body of water partly surrounded by land". (The presence of "gulf" in both lists of synonyms makes one wonder how the data collection process of the GNIS decides how to code a gulf.) Any GNIS names in either of these classes will be assigned the feature code for "Ocean".
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 00
Danger curve.
This code represents an area considered to be dangerous for navigation. When such areas are shown on USGS maps, they are bounded by a dotted black line labelled "Danger Curve".
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 05
Sounding datum.
This code identifies a line shown only on topographicbathymetric maps by a light dotted blue line at the mean low-water line, and which represents the starting elevation (0) for bathymetric contours.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 08
Low-water line.
In areas where the shoreline is undetermined or varies because of meteorological or other conditions, the banks of rivers are shown (starting onshore) by a dashed (indefinite) shoreline, then an "area subject to inundation" fill, then a line of small dashes (the marsh outline symbol) indicating mean low-wter or mean lower low water, then the blue ocean fill. This code identifies the boundary between the marsh symbol and the inundation fill, and represents the mean
low-water or mean lower low-water line.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 11
Beach.
A GNIS Feature Class "beach" (with the listed synonyms "coast", "shore", and "strand") is defined as "the sloping shore along a body of water that is washed by waves or tides and is usually covered by sand or gravel". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 14
Flats (tidal, mud, sand, or gravel).
This code identifies a number of features that fall into the general category of flats; e.g. foreshore flats, areas inside rock reefs, and the area between the shoreline and sounding datum line on topographic-bathymetric maps. Such areas are usually shown on USGS maps as blue with a pattern of small black dots, and are labelled by type -- mud, tidal, gravel, sand, or shell. This feature code is not used for sand dunes, sand in open water, or beach areas on dry land.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 20
Shoal.
A shoal is shown on USGS maps as area outlines with a dotted black line and labelled "Shoal". This code does not apply to 1:100,000-scale maps. It can, however, occur in data derived from the NGNDB. A GNIS Feature Class "bar" (with the listed synonyms "ledge", "reef", "sandbar", "shoal", and "spit") is defined as a "natural accumulation of sand, gravel, or alluvium forming an underwater or exposed embankment". Any GNIS names in this class will be assigned the feature code for "Shoal".
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 25
Rock or group of rocks.
This code identifies a rock or group of rocks in a water area, either exposed or submerged. Exposed rocks are shown on USGS maps as little black asterisks; submerged rocks as black crosses. Sometimes an area full of rocks is shown as a dotted black line surrounding one or more of the rock symbols. In this case, this feature code will identify the line around the rock area.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 30
Submerged InfoBase Sub-Class: 31
Coral reef or rock reef.
A coral or rock reef is shown on USGS maps as a area of black lines and dots labelled "Coral" or "Rock". The reef pattern is filled with blue if the reef is always submerged, or with brown if it is exposed at low water; in the latter case, the area is coded specially.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 35
Exposed at Low Water InfoBase Sub-Class: 36
Sand in open water.
This code identifies an area of sand in other than tidal waters. It is shown on USGS maps as an area of little brown dots.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 40
Channel or boat trail.
A channel in a water area is shown on USGS maps as a double blue line, dashed. This code does not apply to submerged river courses in inundated areas. A boat trail, airboat trail, canoe trail, or wilderness waterway may be shown as a single dashed blue line; on 1:100,000-scale maps they are always shown single. Channels intended for transportation, such as the Intercoastal Waterway, are given a special code for navigable channels.
A GNIS Feature Class "channel" (with the listed synonyms "passage", "reach", "strait", "thoroughfare", and "throughfare") is defined as a "linear deep part of a body of water through which the main volume of water flows and is frequently used as a route for watercraft". Any GNIS names in this class will be assigned the feature code for "Channel".
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 50
Navigable InfoBase Sub-Class: 51
Submerged InfoBase Sub-Class: 52
Gut.
A GNIS Feature Class "gut" (with the listed synonyms "creek", "inlet", and "slough") is defined as a "relatively small coastal waterway connecting larger bodies of water or other waterways". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 55
Harbor.
A GNIS Feature Class "harbor" (with the listed synonyms "hono", "port", "roads", and "roadstead") is defined as a "sheltered area of water where ships or other watercraft can anchor or dock. Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 60
Carolina bay.
A "Carolina Bay" is represented on USGS maps as an elliptically-shaped dashed blue line.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 65
Obstruction area in water area.
This code identifies an obstruction area in a water area shown on USGS maps with a double dashed line and labelled "Pipeline Obstruction Area", "Cable Area", "Pipeline Area", or "Cable-Pipeline Area".
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 70
Spoil area , dredged area, or dump area.
This code designates a feature shown on USGS maps in a variety of ways and labelled "Spoil Area", "Dredged Area", or "Dump Area". They are always areas in open water, usually bounded by a dashed black line (or a pair of such lines), with or without blue tint.
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 75
Holiday area.
This code identifies an inadequate survey area feature shown on USGS maps by a dashed black boundary in a water area, the interior white and labelled "Holiday Area".
ASCII-X Logical Level: 13
InfoBase Class: 30
InfoBase Sub-Class: 80
Lake or pond.
This code identifies a natural non-flowing body of water surrounded by land. It also includes impounded rivers that are labelled "Lake".
Lakes are generally symbolized on USGS maps by a blue-tinted area bounded by a blue line; the boundary line is black anywhere that the shore of the lake is manmade. Intermittent lakes are shown on older maps (compiled prior to December, 1985) as bounded by dashed blue lines; on newer maps the boundary is solid, but the blue tint is replaced by a blue crosshatch pattern. A dry lake is shown by replacing the blue tint or crosshatch with a pattern of brown dots.
Special codes are defined for lakes that are intermittent, dry, or salt.
A GNIS Feature Class "lake" (with the listed synonyms "backwater", "lac", "lagoon", "laguna", "pond", "pool", "resaca", and "waterhole") is defined as a "natural body of inland water". Any GNIS names in this class will be assigned the feature code for "Lake".
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 00Salt InfoBase Sub-Class: 01Intermittent InfoBase Sub-Class: 02Dry InfoBase Sub-Class: 03
Reservoir.
This code identifies either of two sorts of reservoirs -a lake or pond created by a dam, or a (typically masonry) enclosure full of water, rather like a large swimming pool. This code is not used to identify features related to sewage treatment, fish farming, or water filtration.
Any part of the shoreline of a reservoir that is manmade (the dam, for instance) appears twice -- once as part of the "Reservoir" itself, and again as a "Manmade Shoreline".
A GNIS Feature Class "reservoir" (with the listed synonyms "lake" and "tank") is defined as an "artificially impounded body of water". Any GNIS names in this class will be assigned the feature code for "Reservoir".
ASCII-X Logical Level: 11
InfoBase Class: 31 InfoBase Sub-Class: 10
Area to be submerged.
When a dam is under construction and the limits of the intended reservoir are known, the future reservoir is identified with this code. The line depicted is the expected normal pool elevation; if an elevation is associated with the shoreline that defines the limits of the area, an accompanying Annotation record will show the elevation. An area to be submerged is shown on USGS maps as bounded by a dashed blue line and filled with blue crosshatching.
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 20
Inundation area.
This code identifies an area of land between the normal operating level and the high water line in reservoirs or lakes impounded by dams. If an area subject to controlled inundation is shown with an elevation value attached to the line defining the area, the feature will have an associated annotation containing the elevation of the high water line.
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 30
Gravel pit or quarry filled with water.
This code identifies a body of water that has formed naturally in a manmade excavation. Such bodies are shown on USGS maps as lakes or ponds labelled "Gravel Pit" or "Quarry".
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 40
Industrial water impoundment.
This code identifies a lake or pond carrying a label that indicates that the water is collected for industrial use, such as "Industrial Waste Pond" or "Cooling Pond". This does not include the features related to sewage treatment, fish farming, water filtration, or mining.
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 50
Sewage disposal pond or filtration plant.
This code is used for any area that relates to the treatment of sewage. These features are labelled on USGS maps in various ways; e.g. "Sewage Disposal Pond" or "Filtration Bed". The code is also used for an unlabelled pond adjacent to a labelled sewage disposal plant.
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 60
Tailings pond or settling basin.
A tailings pond is shown on USGS maps as bounded by a narrow brown line, filled with a horizontal brown crosshatch or a brown dot pattern, and labelled "Tailings Pond" or "Settling Basin".
ASCII-X Logical Level: 11
InfoBase Class: 31
InfoBase Sub-Class: 70
Shoreline.
This code identifies a natural shoreline, shown on USGS maps by a narrow blue line, but only when the shoreline in question is not part of the boundary of a River, Lake, Ocean, or other areal feature. It is also used for small islands less than .03 inches in diameter at the scale of the source map (250 feet at 1:100,000). Such a shoreline will be coded "intermittent" if the water body it bounds does not always exist.
ASCII-X Logical Level: 13
InfoBase Class: 32
InfoBase Sub-Class: 00Intermittent InfoBase Sub-Class: 01
Manmade shoreline.
This code identifies the shoreline around or along a body of water to indicate that the shoreline is manmade (for instance, a dam, wharf, or levee); such a shoreline is shown on USGS maps as a narrow black line. If the shoreline symbol on the source map is broken by a pier, wharf, or jetty that appears as a single black line, the single-line feature is not digitized as part of the manmade shoreline.
Note that manmade shorelines will often appear twice in the data files, once as a manmade shoreline and again as part of the boundary of some areal feature (a reservoir, for instance).
ASCII-X Logical Level: 11
InfoBase Class: 32
InfoBase Sub-Class: 20
Indefinite shoreline.
This code represents a shoreline whose position cannot be definitely established; it is symbolized on USGS maps as a dashed narrow blue line bounding a blue-tinted area.
ASCII-X Logical Level: 13
InfoBase Class: 32
InfoBase Sub-Class: 40
Apparent shoreline.
This code identifies a coastal shoreline in areas of marsh, grass, or mangrove, or other similar marine vegetation. It represents the outer edge of the vegetation, instead of the mean high-water line, and appears only in data digitized from topographic-bathymetric maps, where it is shown as a very narrow solid blue line.
ASCII-X Logical Level: 13
InfoBase Class: 32
InfoBase Sub-Class: 60
River.
This code identifies all naturally flowing water wider than a stream (i.e. at least .024 inches across at the scale of the source maps, 200 feet at 1:100,000). Rivers are shown on USGS maps as blue areas bounded by blue lines.
Sometimes a natural river course will carry a label identifying it as a ditch; in these cases, it will still be shown as a river, not as a ditch.
When the course of a river is shown in an area of impounded water, the river is digitized as a submerged river. Another unique code is assigned to intermittent river (ones that are only sometimes present).
A special annotation, an arrow "-->" appears with most rivers to designate the direction of flow. The arrow is placed in the river, near the upstream end of whatever portion of the river is present in the current database, and is rotated so that it points generally downstream.
A GNIS Feature Class "stream" (with the listed synonyms "anabranch", "awawa", "bayou", "branch", "brook", "creek", "distributary", "fork", "kill", "pup", "rio", "river", "run", and "slough") is defined as a "linear body of water flowing on the Earth's surface". Any GNIS names in this class will be assigned the feature code for "River". Note that the feature code for "Stream" would probably be more appropriate for some GNIS "streams"; but unfortunately we cannot distinguish between rivers and streams given the vast range of objects covered by the GNIS definition of "stream".
ASCII-X Logical Level: 08
InfoBase Class: 33
InfoBase Sub-Class: 00Intermittent InfoBase Sub-Class: 01Submerged InfoBase Sub-Class: 02
River mile mark.
This code identifies a river mile mark shown on USGS maps as a black cross at the midline of a river and labelled "Mile xxx", where "xxx" is the distance along the river, in miles, from the mark to some reference point on the river.
A river mile mark will always be accompanied by an Annotation record containing the appropriate label, e.g. "Mile 120".
ASCII-X Logical Level: 08
InfoBase Class: 33
InfoBase Sub-Class: 10
Stream.
This code identifies all naturally flowing water narrower than a river (i.e. up to .024 inches across at the scale of the source maps, 200 feet at 1:100,000), except for braided streams. Streams are shown as single blue lines on USGS maps.
Sometimes a natural stream course will carry a label identifying it as a ditch; in these cases, it will still be shown as a stream, not as a ditch. When the course of a stream is shown in an area of impounded water, the stream is digitized as a submerged stream. Another unique code is assigned to intermittent streams (ones that are only sometimes present).
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 20Intermittent InfoBase Sub-Class: 21Submerged InfoBase Sub-Class: 22
Wash or ephemeral drain.
A wash is an ephemeral drainage feature that is normally dry, but can contain runoff from heavy storms or snowmelt for a few hours. It is encoded as a hydrographic feature because it is an integral part of a stream network, generally found in arid areas.
A narrow wash is shown on USGS maps as a single lightweight blue line, like an intermittent stream (which it is). If it is wider than either as two lightweight blue lines or (if much wider) as an area filled with a pattern of light brown dots and labelled "Wash".
This code is not used for any perennial features, even though they may be labelled as washes; instead, they are coded as streams or rivers. Nor is this code used for sand areas adjacent to perennial rivers.
A GNIS Feature Class "arroyo" (with the listed synonyms "coulee", "draw", "gully", and "wash") is defined as a "watercourse or channel through which water may occasionally flow". Any GNIS names in this class will be assigned the feature code for "Wash".
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 30
Braided stream.
A braided stream is a special case where the stream subdivides into interlacing channels. In compilation of USGS maps, when possible, the actual channels are shown; however, if the channels are extremely complex or obscured by vegetation, the outer limit is scribed accurately and the inner channels represented by a conventional pattern of blue lines. The use of pattern versus actual channel is not noted on the map. Therefore, the braided portion of a stream appears in digital data as an outline only.
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 40
Rapids.
Areas of rapids on streams and rivers are represented differently on USGS maps depending on their extent and the size of the stream. On small streams, they are sometimes shown as double blue ticks across the stream, or sometimes as several single blue ticks; on larger rivers, rapids areas are often shown as a pattern of blue ticks in the river parallel to the banks.
A GNIS Feature Class "rapids" (with the listed synonyms "riffle" and "ripple") is defined as a "fast-flowing section of a stream, often shallow and with exposed rock or boulders". Any GNIS names in this class will be assigned the feature code for "Rapids".
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 50
Falls.
Waterfalls on small streams are shown on USGS maps as a single blue tick across the blue line of the stream; on larger rivers they are shown as a line of blue ticks across the river, each tick parallel to the banks.
A GNIS Feature Class "falls" (with the listed synonyms "cascade", "cataract", and "waterfall") is defined as a "perpendicular or very steep fall of water in the course of a stream". Any GNIS names in this class will be assigned the feature code for "Falls".
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 55
Upper origin of stream.
This code identifies a point at the true beginning of a stream, where the narrow blue line symbolizing the stream is first shown. It is not used to mark stream junctures, or to mark streams that exit from a water body.
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 60
Upper origin of stream at water body.
This code identifies a point at which a stream originates either within the limits of or at the point of exit from a water body (like a lake or marsh). It is not used to identify any subsequent exits from water bodies further downstream.
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 61
Stream entering water body.
This code identifies a point at the terminus of a stream where it ends within the limits of or at the perimeter of a water body.
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 62
Stream exiting water body.
This code identifies a point at the terminus of a stream where it begins within the limits of or at the perimeter of a water body, other than at an upper origin of a stream. So if a stream flows into a lake, for instance, and then flows out again, the point of exit would be identified with this code.
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 63
Sink.
A sink is the definite point where a stream flows underground. It is symbolized on USGS maps by a blue Y-shaped mark at the end of the narrow blue line that represents a stream. This code is not used to identify points where strams enter manmade features, such as aqueducts or siphons, or where streams enter and subsequently exit from water bodies.
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 64
Spring or seep.
A spring is shown on USGS maps by a small blue circle with a little squiggly tail; the circle is usually labelled "Spring". If the spring is at the origin of a stream, it will appear twice in the data -once as a spring and once as the upper origin of a stream.
The special code for a hot spring is used when the water flowing from the spring is either hot or contains lots of minerals (alkali, sulphur, etc.).
A GNIS Feature Class "spring" (with the listed synonym "seep") is defined as a "place where underground water flows naturally to the surface of the Earth". Any GNIS names in this class will be assigned the feature code for "Spring".
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 70Hot InfoBase Sub-Class: 71
Nonflowing well.
A water well is shown on USGS maps as a small blue circle. This code identifies water wells that are labelled "Nonflowing Well" or that are not labelled, as happens sometimes especially in areas where wells are numerous.
The special code for a hot well is used when the water from the well is hot or contains lots of minerals (alkali, sulphur, etc.). Other special codes designate wells that are dry or contain salt water.
A GNIS Feature Class "well" is defined as a "manmade shaft or hole in the Earth's surface used to obtain fluid or gaseous materials". On the theory that most oil and gas wells don't have names, and that named wells will therefore usu-
ally be water wells, and that most such wells won't be flowing, any GNIS names in this class will be assigned the feature code for "Nonflowing well".
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 80Dry InfoBase Sub-Class: 81Hot InfoBase Sub-Class: 82Salt InfoBase Sub-Class: 83
Flowing well.
This code identifies a flowing water well, shown on USGS maps as a small blue circle labelled "Flowing Well". It is also used when an unlabelled well symbol appears directly on a stream.
The special code for a hot flowing well is used when the water flowing from the well is hot or contains lots of minerals (alkali, sulphur, etc.).
ASCII-X Logical Level: 09
InfoBase Class: 33
InfoBase Sub-Class: 90Intermittent InfoBase Sub-Class: 91Hot InfoBase Sub-Class: 92
Dam or weir.
There are a variety of symbols used on USGS to show various kinds and sizes of dams and weirs. When a dam is shown on the source map by contouring, this feature code (or more often, the variation designating a dam earthen construction) is applied to the straight segment of the shoreline of the impounded water, parallel to the contouring. When the dam is big enough to appear as an area (and not just a line) on the source map, the outline (but none of the inside markings) of the dam symbol is digitized. A dam may also have an attribute to specify that it carries a road.
The code for an earthen dam is also assigned to any portion of the shoreline of a lake or pond shown on the USGS map by a brown line. It is not applied to the shoreline of a lake or pond that has an intermittent stream attached, for example, a stock pond.
If a dam was under construction at the time the source map was compiled, the dam will be labelled on the map "Under Construction". In this case, in InfoBase format only, the dam entity will include a Text record saying "Under Construction".
A GNIS Feature Class "dam" (with the listed synonyms "breakwater", "dike", and "jetty") is defined as a "water barrier or embankment built across the course of a stream or into a body of water to control and (or) impound the flow of water". Any GNIS names in this class will be assigned the feature code for "Dam".
ASCII-X Logical Level: 11
InfoBase Class: 34
InfoBase Sub-Class: 00Earthen InfoBase Sub-Class: 01Carrying a Road InfoBase Sub-Class: 02
Earthen, Carrying a Road InfoBase Sub-Class: 03
Spillway.
This code identifies a spillway, which is shown on USGS maps in various ways; for instance, as a small circle or dot, by drainage lines either perennial or intermittent, by an arrangement of contour lines, or as a black box. Sometimes a map will have a label "Spillway elevation xxxx"; in this case, an accompanying Annotation record will contain the elevation.
ASCII-X Logical Level: 11
InfoBase Class: 34
InfoBase Sub-Class: 10
Gate (flood, tidal, head, or check).
This code identifies a variety of labelled features used to control or divert the flow of water, shown on USGS maps by a tick or black line.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 15
Canal or ditch.
This code identifies any manmade, flowing water feature used for irrigation, drainage, or transportation; such features are shown on USGS maps with a variety of symbols mostly the same as the symbols used for streams and rivers. Manmade water courses, of various shapes, are included in this code, even if unlabelled. If an obviously natural stream course carries a label identifying it as a ditch, this code is not used.
Some natural streams have portions that appear to have been realigned by man. If the artificial portion of a natural stream is not identified by a label or name change, this code is not used.
Navigable canals used for transportation have a unique code assigned; intermittent or abandoned canals have special codes as well.
A canal that was under construction at the time the source map was compiled will be labelled on the map "Under Construction". In this case, in InfoBase format only, the canal entity will include a Text record saying "Under Construction".
A GNIS Feature Class "Canal" (with the listed synonyms "ditch", and "lateral") is defined as a "manmade waterway used by watercraft or for drainage, irrigation, mining, or water power". Any GNIS names in this class will be assigned the feature code for "Canal".
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 20Navigable InfoBase Sub-Class: 21Intermittent InfoBase Sub-Class: 22Abandoned InfoBase Sub-Class: 23
Canal lock or sluice gate.
This code identifies canal locks or sluice gates, shown by a variety of symbols on USGS maps. If the lock is shown in outline, the outline is digitized and coded with this feature code. Some major rivers have extensive structures shown to scale for which the Lock code is used on the enclosed areas of the structure as well as any linear extent.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 30
Levee.
A GNIS Feature Class "levee" (with the listed synonyms "bank" and "berm") is defined as a "natural or manmade embankment flanking a stream". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 35
Gaging station.
A gaging station is shown on USGS maps a a black circle labelled "Gaging Station" and divided into fourths with the upper left and lower right quadrants coloured in.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 40
Pumping station.
A pumping station is shown on USGS maps either a small black square or (for especially large stations) as a black building outline; in either case, it is labelled "Pumping Station".
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 43
Water intake.
A water intake is shown on USGS maps as a black dot inside a small black circle labelled "Water Intake". This code does not apply to 1:100,000-scale source maps.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 46
Aqueduct or water tunnel.
Aqueducts are symbolized on USGS maps in a variety of ways, all labelled "Aqueduct". Additional codes identify portions of aqueducts that are in tunnels, abandoned, elevated, overpassing another feature, or underground.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 50
Elevated InfoBase Sub-Class: 51
Overpassing InfoBase Sub-Class: 52
In Tunnel InfoBase Sub-Class: 53
Underground InfoBase Sub-Class: 54
Abandoned InfoBase Sub-Class: 55
Flume.
A flume is an artificial open inclined channel that conveys water for a special purpose, and is frequently an elevated feature. Flumes are symbolized on USGS maps by the same group of symbols used for aqueducts, but are labelled "Flume".
Additional codes are used to describe flumes that are
elevated or abandoned.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 60Elevated InfoBase Sub-Class: 61Abandoned InfoBase Sub-Class: 62
Penstock.
A penstock is an underground or exposed pipe conveying water from a canal or a dam to a hydroelectric plant. Penstocks are symbolized on USGS maps by some of the same group of symbols used for aqueducts, but are labelled "Penstock".
A special code is used to designate a penstock in a tunnel.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 65
In Tunnel InfoBase Sub-Class: 66
Siphon.
A siphon is a pipe conveying water to another level, either over or under an obstruction. On 1:24,000-scale USGS maps, siphons are shown as dashed blue lines -the dashes may be omitted if the siphon is less than 200 feet long, and a wing tick or break in the underpassing symbol used instead. On 1:100,000-scale maps, siphons are labelled.
Siphons are frequently (but not always) coded as being either "overpassing" or "underpassing". Usually, if the siphon is not so coded, the object that causes the obstruction will be, and will therefore have a Text record (in InfoBase format only) saying either "Overpassing" or "Underpasssing".
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 70
Overpassing InfoBase Sub-Class: 71
Underpassing InfoBase Sub-Class: 72
Riser.
A riser is a vertical overflow pipe controlling the water level in a reservoir. It is shown on USGS maps as a black dot inside a small black circle labelled "Riser".
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 75
Fish ladder.
There are two ways a fish ladder is shown on USGS maps. It can be merely a labelled part of a stream or river, or it can be a long narrow blackor blue-bounded blue-filled rectangle joined to a stream or river by streams at either end, usually bypassing a marked rapids. In this latter case, if the border of the fish ladder is drawn in black (signifying a manmade construction) the border is coded both as a manmade shoreline and as a fish ladder.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 80
Windmill.
Water-pumping windmills (the only kind that should be included in hydrography) are symbolized on USGS maps by a little triangular base with an "X" at the apex. If the well is salt or dry, the windmill will be labelled "Salt Well" or "Dry Well", and the feature code will vary accordingly.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 85Dry InfoBase Sub-Class: 86Salt InfoBase Sub-Class: 87
Cistern.
A cistern is shown on USGS maps as a small blue circle labelled "Cistern".
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 90
Covered reservoir.
Covered reservoirs are a rare feature, usually made of masonry, and rather like a large swimming pool, filled with water and covered. They are shown on USGS maps as (usually rectangular) grey outlines filled with blue and crosshatched over with narrow closely-spaced black or blue lines. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 09
InfoBase Class: 34
InfoBase Sub-Class: 95
3.2.6 Special-Use Water Features
Salt evaporator.
A salt evaporator is shown on USGS maps as an area of narrow blue lines (the ditches running throughout the evaporator area) with white space in between, the whole complex being labelled "Salt Evaporator". The entire area is represented in TOBIN's database as a salt evaporator, and the ditches represented separately with the feature code for "Canal".
ASCII-X Logical Level: 11
InfoBase Class: 35
InfoBase Sub-Class: 00
Soda evaporator.
A soda evaporator is shown on USGS maps as a white area crossed by blue ditches, the whole area labelled "Soda Evaporator". On the 1:100,000-scale maps a blue dot or blue dash fill is also used.
ASCII-X Logical Level: 11
InfoBase Class: 35
InfoBase Sub-Class: 10
Fish hatchery , fish farm, or fish pond.
A fish hatchery is usually symbolized on USGS maps by a narrow black or blue outline with light blue fill, labelled "Fish Hatchery" or something similar. (The outline is blue if the shoreline of the water body being used for the fish hatchery is natural, black if it is manmade.) The label may vary to indicate the species of fish or the controlling agency. There are frequently ditches or manmade divisions within the boundaries of the hatchery.
ASCII-X Logical Level: 11
InfoBase Class: 35
InfoBase Sub-Class: 20
Duck pond.
This code represents areas shown on the source maps as lakes, ponds, or white areas crossed by blue ditches, whenever the area is labelled "Duck Pond".
ASCII-X Logical Level: 11
InfoBase Class: 35
InfoBase Sub-Class: 30
Rice field.
Rice fields are shown on USGS maps as white areas filled with a triangular pattern of little blue tufts. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 11
InfoBase Class: 35
InfoBase Sub-Class: 40
Cranberry bog.
A cranberry bog is shown on USGS maps as a white area crossed by several blue ditches and labelled "Cranberry Bog".
ASCII-X Logical Level: 11
InfoBase Class: 35
InfoBase Sub-Class: 50
3.2.7 Miscellaneous Hydrography
Marsh , wetland, swamp, or bog.
This code is used for any area shown on USGS maps with the characteristic blue "grass-tufts" pattern. If the background is blue, the marsh is further designated as "submerged"; if it is overprinted with green tint, it is digitized as a "wooded marsh"; it is possible that both conditions will exist, yielding a "submerged wooded marsh". But note that the "wooded" condition is not shown on the 1:100,000-scale source maps, so that the codes reflecting wooded marshes do not apply to data from those sources. There are also codes defined for salt marshes.
A GNIS Feature Class "swamp" (with the listed synonyms "bog", "cienaga", "marais", "marsh", and "pocosin") is defined as a "poorly drained wetland, fresh or saltwater, wooded or grassy, possibly covered with open water". Any GNIS names in this class will be assigned the feature code for "Marsh".
ASCII-X Logical Level: 11
InfoBase Class: 36
InfoBase Sub-Class: 00Submerged InfoBase Sub-Class: 01Wooded InfoBase Sub-Class: 02Submerged and Wooded InfoBase Sub-Class: 03Salt InfoBase Sub-Class: 04Submerged and Salt InfoBase Sub-Class: 05
Mangrove area.
A water area wooded with mangroves is shown on USGS maps by a dense blue pattern of leaves with pale green overtint.
ASCII-X Logical Level: 11
InfoBase Class: 36
InfoBase Sub-Class: 20
Glacier or snowfield.
This code represents any area permanently covered with snow or ice. USGS maps represent glaciers and their contouring in various ways.
A GNIS Feature Class "glacier" (with the listed synonyms "icefield", "ice patch", and "snow patch") is defined as a "body or stram of ice moving outward and downslope from an area of accumulation; an area of relatively permanent snow or ice on the top or side of a mountain or mountainous area". Any GNIS names in this class will be assigned the feature code for "Glacier".
ASCII-X Logical Level: 11
InfoBase Class: 36
InfoBase Sub-Class: 40
Glacial crevasse.
Glacial crevasses are shown on USGS maps as blue lines of various weights on the surfaces of glaciers, and labelled "Crevasses". This code identifies either individual crevasse lines (if the crevasse area contains fewer than four lines) or the area itself. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 11
InfoBase Class: 36
InfoBase Sub-Class: 50
Geyser or vent.
This code identifies a special type of spring that ejects hot water or steam periodically; this includes gas vents, mud pots, fumaroles, and steam vents. Geysers are shown on USGS maps as a small blue circle labelled "Geyser".
A GNIS Feature Class "geyser" is defined as an "eruptive spring from which hot water and (or) steam and in some cases mud are periodically thrown". Any GNIS names in this class will be assigned the feature code for "Geyser".
ASCII-X Logical Level: 09
InfoBase Class: 36
InfoBase Sub-Class: 60
Alkali flat.
Alkali flats are symbolized on USGS maps by a white area bounded by a dashed blue line and labelled "Alkali Flat".
ASCII-X Logical Level: 11
InfoBase Class: 36
InfoBase Sub-Class: 70
Roads are classified by the USGS into five classes; the definitions are roughly as follows:
Class 1A primary highway with a hard (paved) surface. (Obviously, there is some room for subjective judgement in deciding which routes are primary.) In general, this includes all Interstate and United States highways.
Class 2A secondary highway with a hard (paved) surface. (Again, the definition of "secondary" route is less than unambiguous.) Most State highways fall into this class, and many County roads.
Class 3A light-duty road or street with a hard or improved dirt surface. Most city streets and many County roads fall into this class.
Class 4Roads with unimproved dirt surfaces.
Class 5Trails, including those fit only for fourwheel drive vehicles, and old railroad grades where the tracks have been dismantled. Also foot trails, pack trails, and bicycle trails.
Roads are shown on USGS maps in a huge variety of ways, depending on the class of the road, whether it's in an urban or rural area, the scale and series of the map, the actual size of the road, the number of lanes, the presence of a dividing wall or median strip, etc.
For TOBIN's purposes, all roads of the same class are assigned the same group of feature codes. This scheme preserves all the information available in the data digitized from 1:100,000-scale maps. There will be some additional data available in the DLGs from 1:24,000-scale maps (e.g. the presence or absence of a dividing wall in a dual highway, the designation of some roads as "one-way", the actual width of the roadway when it has been scribed to scale on the source map, and so on); so the set of feature codes may need to be refined and expanded if it becomes necessary to represent the whole range of data from large-scale source maps.
Many roads and highways will be accompanied by an Annotation record containing the name of the road. The following prefixes and abbreviations are used in highway names:
I- Interstate route number
US U. S. route number
SR State route number
Res Reservation, park, or military route number
Cty County route number
ALT Alternate
BR Business route
BYP Bypass
CONN Connector
LOOP Loop
SPUR Spur
TR Truck route
Class 1 road.
A class 1 road is a primary highway with a hard surface. In general, this includes all Interstate and United States highways.
Special feature codes are defined to represent those portions of class 1 roads that are in tunnels, on bridges, elevated, or underpassing or overpassing some other feature.
A class 1 road marked as being under construction at the time of compilation of the source map will have an accompanying Text record (in InfoBase format only) saying "Under Construction". Similar Text records will accompany any class 1 road marked as being a "Toll Road", "Proposed", or "Double-decked" (i.e. constructed over another road or on a two-level bridge). Note that these last two conditions do not apply to data digitized from 1:100,000-scale maps.
The DLG definitions include attribute codes for specifying the actual number of lanes a road has. These attribute codes seem to be used only infrequently. If one should occur, a Text record will accompany the road (in InfoBase format only) saying, for instance "4 Lanes" (or however many there were). This lane-count record can be applied to any class of road, but is most common on class 1 and class 2 highways.
ASCII-X Logical Level: 14
InfoBase Class: 40
InfoBase Sub-Class: 10
Elevated InfoBase Sub-Class: 11
On Bridge InfoBase Sub-Class: 12
In Tunnel InfoBase Sub-Class: 13
Overpassing InfoBase Sub-Class: 14
Underpassing InfoBase Sub-Class: 15
Class 2 road.
A class 2 road is a secondary highway with a hard surface. Most State highways fall into this class, as well as many County roads.
Special feature codes are defined to represent those portions of class 2 roads that are in tunnels, on bridges, elevated, or underpassing or overpassing some other feature.
A class 2 road marked as being under construction at the time of compilation of the source map will have an accompanying Text record saying "Under Construction". Similar Text records will accompany any class 2 road marked as being a "Toll Road", "Proposed", or "Double-decked" (i.e. constructed over another road or on a two-level bridge). Note that these last two conditions do not apply to data digitized from 1:100,000-scale maps.
See the discussion under "Class 1 road" of Text records containing the actual number of lanes in a road.
ASCII-X Logical Level: 15
InfoBase Class: 40
InfoBase Sub-Class: 20Elevated InfoBase Sub-Class: 21On Bridge InfoBase Sub-Class: 22In Tunnel InfoBase Sub-Class: 23Overpassing InfoBase Sub-Class: 24Underpassing InfoBase Sub-Class: 25
Class 3 road.
A class 3 road is a light-duty road or street with a hard or improved dirt surface. Most city streets and many County roads fall into this class.
Special feature codes are defined to represent those portions of class 3 roads that are in tunnels, on bridges, elevated, or underpassing or overpassing some other feature.
A road that runs through a service facility or rest area (areas labelled on 1:24,000-scale maps as "Service Facility", "Service Area", "Service Plaza", "Rest Area", or "Roadside Park", but usually unlabelled and scribed to scale on 1:100,000-scale maps), usually a class 3 or class 4 road, also is distinguished by a special feature code.
A class 3 road marked as being under construction at the time of compilation of the source map will have an accompanying Text record saying "Under Construction". A similar Text record will accompany any class 3 road marked as being "Double-decked" (i.e. constructed over another road or on a two-level bridge). Note that this condition does not apply to data digitized from 1:100,000-scale maps.
A road or street whose use is restricted (such as a road through a military reservation, a road or trail through a ranch, or a fire road in a forest preserve) is labelled "Private" or "Restricted" on USGS maps. The records describing such roads are accompanied in the InfoBase format by a Text record saying "Private". This condition also applies to a road or trail that is not itself labelled, but is accessible only by way of a road labelled "Private" or "Restricted".
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 30Elevated InfoBase Sub-Class: 31On Bridge InfoBase Sub-Class: 32In Tunnel InfoBase Sub-Class: 33Overpassing InfoBase Sub-Class: 34Underpassing InfoBase Sub-Class: 35
In Service Facility InfoBase Sub-Class: 36
Class 4 road.
Class 4 roads are those roads and streets with unimproved dirt surfaces.
Special feature codes are defined to represent those portions of class 4 roads that are in fords (submerged) or underpassing some other feature. Note that the "In a Ford" condition does not apply to 1:100,000-scale maps.
See above under "Class 3 road" for an explanation of roads coded as being in service facilities; also for those designated as restricted or private.
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 40Underpassing InfoBase Sub-Class: 41In Ford InfoBase Sub-Class: 42In Service Facility InfoBase Sub-Class: 43
Class 5 road.
Class 5 roads are better designated "trails", including those fit only for four-wheel drive vehicles, old railroad grades where the tracks have been dismantled, foot trails, pack trails, and bicycle trails.
A special code is defined for class 5 roads marked "Jeep" or "4WD" on the source maps. Also defined are special feature codes for trails marked "Old Railroad Grade" (meaning that the tracks have actually been dismantled, but that the grade may still be usable for some transportation purposes -- in this case no feature on the Railroad data layer is coded), and for those portions of trails that are in fords. This last condition does not apply to 1:100,000-scale maps.
A GNIS Feature Class "trail" (with the listed synonyms "jeep trail", "path", and "ski trail") is defined as a "route for passage from one point to another; does not include roads or highways". Any GNIS names in this class will be assigned the feature code for "Class 5 Road".
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 50Four-Wheel Drive InfoBase Sub-Class: 51
Old Railroad Grade InfoBase Sub-Class: 52
In Ford InfoBase Sub-Class: 53
Road in transition.
This code identifies a centerline of a section of any road where a change in the road width occurs, and the transitional section is equal to or greater than 0.25 inches in length at the scale of the source map (500 feet at 1:24,000, or 2083 feet at 1:100,000).
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 70
Nonstandard section of road.
This code describes the edges of a section of road that is nonstandard, i.e. wider than normal, or with non-parallel edges, or varying in width, or whatever. Normally the road will be represented in the data in its own right, and any lines designated "nonstandard section of road" will not be
assigned a route number.
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 75
Cloverleaf or interchange.
This code identifies an intersection of roads and ramps at a cloverleaf or interchange. It generally does not carry a route number.
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 80
Traffic circle.
This code identifies the marked-off area at the center of a junction of three or more roads that forms a circle around which traffic normally moves in one direction; it should not be confused with a cul-de-sac.
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 85
Crossing.
A GNIS Feature Class "crossing" (with the listed synonyms "overpass", and "underpass") is defined as "a place where two or more routes of transportation form a junction of intersection". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 16
InfoBase Class: 40
InfoBase Sub-Class: 90
Gate.
This code identifies the entrance to or beginning of a controlled public access road, other than a tollgate. The code does not apply to 1:100,000-scale maps; it is shown on standard quadrangles as a straight black tick mark crossing a road and labelled "Gate".
ASCII-X Logical Level: 16
InfoBase Class: 41
InfoBase Sub-Class: 00
Cul-de-sac.
A cul-de-sac is shown on USGS maps by a small circular road area at the end of a road, either with or without a central island. This code identifies only those cul-de-sacs that have no central island shown -- if the island is shown, the cul-de-sac is coded as a regular road going around in a circle, not as a cul-de-sac.
ASCII-X Logical Level: 16
InfoBase Class: 41
InfoBase Sub-Class: 10
Dead end.
This code identifies a dead-end street that is shown on USGS maps as closed with a black tick mark. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 16
InfoBase Class: 41
InfoBase Sub-Class: 20
Bridge abutment.
This code identifies either end of a bridge, shown on USGS maps by a wing tick (a little black arc crossing the line of a road).
ASCII-X Logical Level: 16
InfoBase Class: 42
InfoBase Sub-Class: 00
Drawbridge.
On some USGS maps, a drawbridge is shown as a road crossing a river, with a circle on the road midway across. This code identifies the spot of the circle in the drawbridge symbol, and does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 16
InfoBase Class: 42
InfoBase Sub-Class: 10
Covered bridge.
This code describes a feature that crosses an obstruction, usually a body of water, and is labelled "Covered Bridge" on the source map
ASCII-X Logical Level: 16InfoBase Class: 42
InfoBase Sub-Class: 20
Footbridge.
A footbridge is shown on USGS maps as a very narrow solid black line crossing a body of water, usually in line with a trail or footpath (a class 5 road, usually shown as a very narrow dashed black line). This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 16
InfoBase Class: 42
InfoBase Sub-Class: 30
Road ferry crossing.
This code describes a line digitized from bank to bank along a ferry crossing route; it is shown on USGS maps as a dashed black line crossing a body of water between two roads and labelled "Ferry".
ASCII-X Logical Level: 16
InfoBase Class: 42
InfoBase Sub-Class: 40
Tunnel portal.
This code identifies either end of a tunnel, shown on USGS maps by a wing tick. The tunnel itself is shown as a dashed double black line.
ASCII-X Logical Level: 16
InfoBase Class: 42
InfoBase Sub-Class: 50
3.3.6 Miscellaneous Road Features
Parking area.
This code describes a line digitized along the perimeter of a parking area. Such areas on USGS maps are usually labelled "Parking Area" and coloured grey. Many parking areas, however, are not labelled, but are obvious because of their shape and proximity to such features as retail centers and stadiums. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 16
InfoBase Class: 43
InfoBase Sub-Class: 00
Tollgate or toll plaza.
A tollgate is shown on USGS maps by a black tick mark placed across a road and labelled "Tollgate". This code identifies such a spot; it is also used for a line digitized around an area on a toll road that is labelled "Toll Plaza".
ASCII-X Logical Level: 16
InfoBase Class: 43
InfoBase Sub-Class: 10
Weigh station or agricultural inspection station.
This code identifies a feature labelled "Weigh Station" or "Agricultural Inspection Station". On 1:100,000-scale USGS maps, the feature is shown as a narrow road-coloured line branching off from, running parallel to, and then rejoining a highway. On 1:24,000-scale maps several treatments may be used, depending on the size of the feature. In data from these maps, this code can represent either the roads in and around the station, or the perimeter of the station area, or the placement of the buildings that make up the station -it all depends on how the weigh station was shown on the
source map.
ASCII-X Logical Level: 16
InfoBase Class: 43
InfoBase Sub-Class: 20
Railroad.
This code describes a railroad line. Railroad lines are shown on USGS maps by a variety of solid and dashed single and double black lines, all distinguished by periodic tick marks.
Special feature codes are defined for those portions of railroads that are in a tunnel (shown on 1:100,000-scale maps by single and on 1:24,000-scale maps as double dashed black lines with wing ticks at either end), overpassing or underpassing some other feature, inside a snowshed or some other kind of building (shown as a black building outline filled with black crosshatching), elevated, or on a drawbridge (shown as a railroad crossing a river, with a black circle midway across). The "On Drawbridge" code does not apply to 1:100,000-scale maps.
Unless the railroad is specified as having more than one track, it is assumed to be a single track. If a multiple track railroad should occur, a Text record will accompany the railroad (in InfoBase format only) saying, for instance "2 Tracks" (or however many there were). Multiple-track railroads are also distinguished from single tracks by the symbol used -on 1:24,000-scale maps (for standard gague lines) multiple tracks are shown by a doubled main line on the railroad symbol, on 1:100,000-scale maps (and at 1:24,000-scale for narrow gague) by doubled tick marks.
Similarly, the railroad is assumed to be standard gague unless it is marked otherwise. If the railroad is narrow gague, a Text record will contain the words "Narrow Gague" (in InfoBase format only). Narrow gague lines are distinguished from standard gague lines on USGS maps by having shorter tick marks alternating from side to side of the main line shown.
Sometimes a railroad will have an accompanying (InfoBase) Text record saying either "Abandoned" or "Dismantled". An abandoned railroad is one for which the tracks and roadbed are still in place, although unused and of varying conditions. A dismantled railroad is one whose tracks have been removed. Many railroads that are dismantled are labelled "Old Railroad Grade" and are used and symbolized not as railroads, but as class 5 roads (trails) in the Roads and Trails data layer. Abandoned tracks, as well as being labelled "Abandoned", are indicated on USGS maps by the main rail line having short periodic gaps. Only features actually labelled "Dismantled" on the source maps are coded as dismantled.
Other possible Text records are "Under Construction", "Rapid Transit", "Private", and "U. S. Government".
ASCII-X Logical Level: 18
InfoBase Class: 60
InfoBase Sub-Class: 00Underpassing InfoBase Sub-Class: 01Overpassing InfoBase Sub-Class: 02
In Tunnel InfoBase Sub-Class: 03
In Snowshed or Building InfoBase Sub-Class: 04
Elevated InfoBase Sub-Class: 05
On Drawbridge InfoBase Sub-Class: 06
Railroad siding or spur.
This code describes a railroad siding, one or more single tracks branching off from a main line of a railroad. It also describes a spur that is a single track that diverges from the main track and leads to some facility such as an industrial plant. Both sidings and spurs are shown on USGS maps by a very lightweight railroad symbol. A railroad siding or spur may be of any length.
The same set of additional special feature codes are defined for sidings as for regular railroad lines, and the same set of Text records are possible in InfoBase format.
ASCII-X Logical Level: 18
InfoBase Class: 60
InfoBase Sub-Class: 20Underpassing InfoBase Sub-Class: 21Overpassing InfoBase Sub-Class: 22In Tunnel InfoBase Sub-Class: 23In Snowshed or Building InfoBase Sub-Class: 24Elevated InfoBase Sub-Class: 25On Drawbridge InfoBase Sub-Class: 26
Carline.
A carline is shown on USGS maps by a symbol like that for a regular railroad, but with the tick marks spaced only half as far apart. Not all carlines are shown on USGS maps -the instructions for 1:100,000-scale maps say "Show landmark carlines only", and those for 1:24,000-scale maps say "Do not show in urban areas, streets, or roads."
Abandoned carlines, for which a special code is defined, are labelled "Abandoned" on the source maps, and further distinguished by having periodic gaps in the main line. A special feature code also exists for a carline labelled "Dismantled".
ASCII-X Logical Level: 18
InfoBase Class: 60
InfoBase Sub-Class: 40Abandoned InfoBase Sub-Class: 41Dismantled InfoBase Sub-Class: 42
Cog railroad , incline railway, or logging tram.
This code describes various special-purpose railroads, shown on USGS maps by a single dashed black line, labelled "Cog Railway", "Incline Railway", or "Logging Tram".
Special codes are defined for such features when they are
additionally labelled either "Abandoned" or "Dismantled".
ASCII-X Logical Level: 18
InfoBase Class: 60
InfoBase Sub-Class: 50Abandoned InfoBase Sub-Class: 51Dismantled InfoBase Sub-Class: 52
Crossover.
This code identifies a central point of a crossover between two railroad tracks; the crossover is shown on USGS maps as a diagonal line connecting two tracks. This code is not used to identify features inside a railroad yard.
ASCII-X Logical Level: 18
InfoBase Class: 60
InfoBase Sub-Class: 60
Yard.
This code identifies the perimeter of a rail yard, following the outline of the outermost tracks, which are the only ones whose position is shown accurately on USGS maps, the other lines begin represented by a pattern not corresponding to the actual distribution of tracks within the yard. Large railroad yards may have interior islands or clear areas that are not occupied by tracks, or (on maps) by the track pattern. These internal areas are also shown with this code, following the line of the innermost tracks.
ASCII-X Logical Level: 18
InfoBase Class: 61
InfoBase Sub-Class: 00
Turntable.
This code identifies a railroad turntable. Turntables are shown on USGS maps either as a black circle containing a black diagonal line, or are drawn to scale. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 18
InfoBase Class: 61
InfoBase Sub-Class: 10
Roundhouse.
This code represents the outline of a railroad roundhouse.
ASCII-X Logical Level: 18
InfoBase Class: 61
InfoBase Sub-Class: 20
Railroad station.
This code identifies a railroad station, shown on USGS maps either as a small black rectangle on a rail line (when no siding, building, or other identifying feature is shown) or as a black building outline.
ASCII-X Logical Level: 18
InfoBase Class: 61
InfoBase Sub-Class: 30
3.4.3 Miscellaneous Railroad Features
Bridge abutment.
This code describes either end of a railroad bridge, shown on USGS maps by a wing tick (a little black arc crossing the line of the railroad).
ASCII-X Logical Level: 18
InfoBase Class: 62
InfoBase Sub-Class: 00
Tunnel portal.
This code describes either end of a railroad tunnel. The railroad tunnel itself is shown on USGS maps as a dashed black line with wing ticks at either end. The dashed line is double on 1:24,000-scale maps and single on 1:100,000scale maps.
ASCII-X Logical Level: 18
InfoBase Class: 62
InfoBase Sub-Class: 10
Drawbridge.
On some USGS maps, a railroad drawbridge is shown as a railroad crossing a river, with a circle on the railroad midway across. This code identifies the spot of the circle in the
drawbridge symbol, and does not apply to 1:100,000-scale
maps.
ASCII-X Logical Level: 18
InfoBase Class: 62
InfoBase Sub-Class: 20
Railroad ferry crossing.
This code describes a line digitized from bank to bank along a railroad ferry crossing route; it is shown on USGS maps as a dashed black line crossing a body of water between two railroads and labelled "Ferry".
ASCII-X Logical Level: 18
InfoBase Class: 62
InfoBase Sub-Class: 30
3.5 Pipes, Transmission Lines, and Miscellaneous Transportation
For all feature codes in this data layer, if the source map shows the feature labelled "Under Construction" or "Abandoned" or "Closed", a Text record will accompany the entity (in InfoBase format only) containing the same words.
3.5.1 Electrical Power Features
Power transmission line.
A power transmission line is shown on USGS maps as a narrow black line with periodic small black squares on it. The steel or concrete towers are shown as open black squares on the line. An underground transmission line is labelled "Underground"; a special code is defined to represent this case.
ASCII-X Logical Level: 24
InfoBase Class: 70
InfoBase Sub-Class: 00Underground InfoBase Sub-Class: 01
Tower on transmission line.
This code describes a steel or concrete tower located on a transmission line, shown on USGS maps as a small open black square.
ASCII-X Logical Level: 24
InfoBase Class: 70
InfoBase Sub-Class: 20
Power station end of transmission line.
This code identifies the end of a transmission line that terminates at a power station, substation, or hydroelectric plant. It is not used when the termination point of the transmission line is not identified.
ASCII-X Logical Level: 24
InfoBase Class: 70
InfoBase Sub-Class: 40
Power station or power plant.
This code describes a power station that is shown on the source map by a building symbol appropriate to the size of the structure and labelled "Power Plant" or "Power Station". A special code is defined to represent those power plants labelled "Nuclear" on the source map.
ASCII-X Logical Level: 24
InfoBase Class: 70
InfoBase Sub-Class: 60Nuclear InfoBase Sub-Class: 61
Hydroelectric plant.
This code describes a hydroelectric station that is shown on the source map by a building symbol appropriate to the size of the structure and labelled "Hydroelectric Plant".
ASCII-X Logical Level: 24
InfoBase Class: 70
InfoBase Sub-Class: 70
Substation.
This code describes a substation. It is shown on USGS maps in either of two ways: a small substation appears as a small open black square, a large one as a dashed black line (showing the perimeter of the substation) possibly enclosing a group of buildings. (In this latter case, the feature code for the substation refers to the perimeter, and the buildings themselves are represented in the Manmade Features data layer.) In any case, the substation will be labelled on the source map either "Substation" or "Substa."
ASCII-X Logical Level: 24
InfoBase Class: 70
InfoBase Sub-Class: 80
Pipeline.
This code describes a pipeline; special codes are defined for pipelines that are submerged or above ground. (Unless specified otherwise, a pipeline is assumed to be underground.)
A pipeline is shown on USGS maps as dashed black line; on 1:24,000-scale maps it is labelled "Pipeline", but on 1:100,000-scale maps is unlabelled. If it is above ground, the line is solid and the label (at either scale) says "Aboveground Pipeline". Pipelines shown crossing bodies of water are assumed to be submerged.
ASCII-X Logical Level: 17
InfoBase Class: 71
InfoBase Sub-Class: 00Above Ground InfoBase Sub-Class: 01Submerged InfoBase Sub-Class: 02
Source end of pipeline.
This code identifies the end of a pipeline that terminates at an oil or gas field. The code is used only when the area on the source map that is labelled "Oil Field" or "Gas Field" is not separated from the termination point by any other feature.
ASCII-X Logical Level: 17
InfoBase Class: 71
InfoBase Sub-Class: 20
Destination end of pipeline.
This code identifies the end of a pipeline that terminates at a refinery or depot (so labelled on the source map), or at a group of tanks that make up a tank farm, whether labelled or not.
ASCII-X Logical Level: 17
InfoBase Class: 71
InfoBase Sub-Class: 30
Pumping station or compressor station.
This code describes a pumping station or compressor station associated with a gas or oil pipeline. These are shown on USGS maps in either of two ways, as a small open black square, or as a dashed black line (showing the perimeter of the station) possibly enclosing a group of buildings. (In this latter case, the feature code for the pumping station refers to the perimeter, and the buildings themselves are represented in the Manmade Features data layer.) In any case, the station will be labelled "Pumping Station" on the source map.
ASCII-X Logical Level: 17
InfoBase Class: 71
InfoBase Sub-Class: 50
Measuring station or valve station.
This code describes a measuring station or valve station associated with a gas or oil pipeline that is shown on the source map by a building symbol appropriate to the size of the structure and labelled.
ASCII-X Logical Level: 17
InfoBase Class: 71
InfoBase Sub-Class: 60
3.5.3 Miscellaneous Transportation Features
Telephone line or telegraph line.
A telephone or telegraph line is shown on 1:24,000-scale USGS maps as a dashed black line, and on 1:100,000-scale maps as a solid black line with periodic black squares on it. At either scale, the line is labelled either "Telephone" or "Telegraph"; no distinction is made in feature codes between telephone and telegraph lines.
ASCII-X Logical Level: 24
InfoBase Class: 72
InfoBase Sub-Class: 00
Aerial tramway , monorail, or ski lift.
This code describes an aerial tramway, monorail, or ski lift, shown on USGS maps as a dashed black line labelled as to type.
ASCII-X Logical Level: 16
InfoBase Class: 72
InfoBase Sub-Class: 20
Bridge.
A GNIS Feature Class "bridge" (with the listed synonyms "causeway", "overpass", and "trestle") is defined as a "manmade structure carrying a trail, road, or other transportation system across a body of water or depression". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 16
InfoBase Class: 72
InfoBase Sub-Class: 40
Tunnel.
A GNIS Feature Class "tunnel" is defined as a "linear underground passageway open at both ends". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 16
InfoBase Class: 72
InfoBase Sub-Class: 50
Airport or landing strip.
This code is used to describe a landing strip, an airport, or the perimeter of an airport. These features are rather complicated, and are shown in a variety of ways on USGS
maps.
On 1:100,000-scale maps, any runway longer than 2500 feet in length is shown as a dark grey area. If it is wider than 83 feet, it is scribed to scale, and the entity described by
this feature code will follow the outline of the runway as shown. If the runway is narrower than 83 feet, it will be shown on the map by a line of .01 inches thickness; in this case, the feature will be a single line, not the outline.
On 1:24,000-scale maps, on the other hand, this feature code represents the outline of the runway as drawn; but note that any runway narrower than 40 feet is shown as 40 feet wide. On these large-scale maps the extent of the airport may also be shown by a dashed black line around the perimeter; or the extent of the taxiways and aprons may be shown as a lightweight solid black line. When any of these features are thus shown, this feature code is used to show all such features -aprons, taxiways, airport perimeters, and runways. If it is impossible on the source map to distinguish the runway, taxiway, or apron boundaries form adjacent access roads or other features, only the perimeter of the entire airport is shown.
An unimproved (loose or turf surface) landing strip is shown on USGS maps as a dashed black outline labelled "Landing Strip". A special feature code is defined for this case. This special code does not apply to 1:100,000-scale maps.
A GNIS Feature Class "airport" (with the listed synonyms "airfield", "airstrip", "landing field", and "landing strip") is defined as a "manmade feature maintained for the use of aircraft". Any GNIS names in this class will be assigned the feature code for "Airport".
ASCII-X Logical Level: 16
InfoBase Class: 73
InfoBase Sub-Class: 00Unimproved Surface InfoBase Sub-Class: 01
Heliport.
This code describes a heliport facility. Small heliports are shown on USGS maps as a small black circle (containing a black dot on 1:24,000-scale maps) and labelled; large heliports are shown on 1:24,000-scale maps by a solid black line outlining the perimeter, and on 1:100,000-scale maps as a dark grey area.
ASCII-X Logical Level: 16
InfoBase Class: 73
InfoBase Sub-Class: 30
Seaplane anchorage.
A feature code for "Seaplane anchorage" is defined in the relevant DLG documents, but no description is available (beyond the fact that such a feature consists of a single point), and no symbol for a seaplane anchorage is defined in any of the USGS compilations of map symbols. So this code may not, in fact, ever occur.
ASCII-X Logical Level: 16
InfoBase Class: 73
InfoBase Sub-Class: 60
Seaplane ramp or seaplane landing area.
This code describes a seaplane ramp or landing area that is shown on USGS maps by a variety of treatments and labelled. The feature is digitized by a center lie in a landing strip or a line around the perimeter of a ramp, depending on how the feature appears on the source maps. This code does not apply to 1:100,000-scale maps.
ASCII-X Logical Level: 16
InfoBase Class: 73
InfoBase Sub-Class: 70
Launch complex.
This code describes a feature that is labelled "Launch Complex". There is no standard symbol for this feature class. If the limit of the complex is discernible, a line is digitized along the perimeter; otherwise a single point is shown in the approximate center of the facility.
ASCII-X Logical Level: 16
InfoBase Class: 73
InfoBase Sub-Class: 90
The following feature codes are currently used only for certain feature names derived from the GNIS NGNDB files. TOBIN does not at this time process or distribute any DLG data in the Manmade Features layer.
Building.
A GNIS Feature Class "building" is defined as "a manmade structure with walls and a roof for protection of people and (or) materials, but not including church, hospital, or school". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 01
Cemetery.
A GNIS Feature Class "cemetery" (with the listed synonyms "burial", "burying ground", "grave", and "memorial garden" -and surely "churchyard" and "graveyard" should have been included on the list) is defined as "a place or area for burying the dead". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 02
Church.
A GNIS Feature Class "church" (with the listed synonyms "chapel", "mosque", "synagogue", "tabernacle", and "temple") is defined as a "building used for religious worship". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 03
Hospital.
A GNIS Feature Class "hospital" (with the listed synonym "infirmary") is defined as a "building where the sick and injured may receive medical or surgical attention". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 04
Locale.
A GNIS Feature Class "locale" (with the listed synonyms "battlefield", "crossroad", "camp", "farm", "ghost town", "landing", "railroad siding", "ranch", "ruins", "site", "station", and "windmill") is defined as a "place at which there is or was human activity; it does not include populated places, mines, and dams". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 05
Mine.
A GNIS Feature Class "mine" (with the listed synonyms "pit", "quarry", and "shaft") is defined as a "place or area from which commercial minerals are or were removed from the Earth; not including oilfield". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 06
Oilfield.
A GNIS Feature Class "oilfield" is defined as an "area where petroleum is or was removed from the Earth". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 07
Other.
A GNIS Feature Class "other" is defined as a "category for miscellaneous named manmade entities that cannot readily be placed in the other feature classes" defined. Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 08
Populated place.
A GNIS Feature Class "ppl" -an abbreviation for "populated place" -(with the listed synonyms "city", "settlement", "town", and "village") is defined as a "place or area with clustered or scattered buildings and a permanent human population". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 07
InfoBase Class: 80
InfoBase Sub-Class: 09
School.
A GNIS Feature Class "school" (with the listed synonyms "academy", "college", "high school", and "university") is defined as a "building or group of buildings used as an institution for study, teaching, and learning. Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 10
Tower.
A GNIS Feature Class "tower" is defined as "a manmade structure, higher than its diameter, generally used for observation, storage, or electronic transmission". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 80
InfoBase Sub-Class: 11
The following feature codes are currently used only for certain feature names derived from the GNIS NGNDB files. Except insofar as they are accidentally represented or implied by elements in the hypsography, hydrography, and land cover layers, features in this layer are not currently
collected or represented in the NDCDB.
Area.
A GNIS Feature Class "area" (with the listed synonyms "badlands", "barren", "delta", "fan", and "garden") is defined as "any one of several areally extensive natural features not included in other categories". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 01
Island.
A GNIS Feature Class "island" (with the listed synonyms "archipelago", "atoll", "cay", "hammock", "hummock", "isla", "isle", "key", "moku", and "rock") is defined as an "area of dry or relatively dry land surrounded by water or low wetland. Any GNIS names in this class will be assigned this
feature code.
ASCII-X Logical Level: 10
InfoBase Class: 90
InfoBase Sub-Class: 02
Plain.
A GNIS Feature Class "plain" (with the listed synonyms "grassland", "highland", "kula", "plateau", and "upland") is defined as "a region of general uniform slope, comparatively level and of considerable extent". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 03
Range.
A GNIS Feature Class "range" (with the listed synonyms "cordillera" and "sierra") is defined as a "chain of hills or mountains; a somewhat linear, complex mountainous or hilly area". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 04
Ridge.
A GNIS Feature Class "ridge" (with the listed synonyms "crest", "cuesta", "escarpment", "hogback", "lae", "rim", and "spur") is defined as an "elevation with a narrow, elongated crest which can be part of a hill or mountain". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 05
Summit.
A GNIS Feature Class "summit" (with the listed synonyms "ahu", "berg", "bald", "butte", "cerro", "colina", "cone", "cumbre", "dome", "head", "hill", "horn", "knob", "knoll", "mauna", "mesa", "mesita", "mound", "mount", "mountain", "peak", "puu", "rock", "sugarloaf", "table", and "volcano") is defined as a "prominent elevation rising above the surrounding level of the Earth's surface; does not include pillars, ridges, or ranges". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 06
Valley.
A GNIS Feature Class "valley" (with the listed synonyms "barranca", "canyon", "chasm", "cove", "draw", "glen", "gorge", "gulch", "gulf", "hollow", and "ravine") is defined as a "linear depression in the Earth's surface that generally slopes from one end to the other". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 07
Woods.
A GNIS Feature Class "woods" is defined as a "small area covered with a dense growth of trees; does not include an area of trees under the administration of a political agency". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 08
Arch.
A GNIS Feature Class "arch" (with the listed synonyms "bridge", "natural bridge", and "sea arch") is defined as a "natural arch-like opening in a rock mass". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 21
Bench.
A GNIS Feature Class "bench" (with the listed synonym "level") is defined as an "area of relatively level land on the flank of an elevation such as a hill, ridge, or mountain where the slope of the land rises on one side and descends on the opposite side". Any GNIS names in this class will be assigned this feature code.
ASCII-X Logical Level: 26
InfoBase Class: 90
InfoBase Sub-Class: 22
Bend.
A GNIS Feature Class "bend" (with the listed synonyms "bottom", "loop", and "meander") is defined as a "curve in the course of a stream and (or) the land within the curve; a curve in a linear body of water". Any GNI